Evolutionary upgrade for the multi-mission radioisotope thermoelectric generator (MMRTG)

Abstract

Advanced thermoelectric materials developed over the last 10 years have opened up a number of radioisotope generator design options for deep space and planetary exploration. Publications over the last several years have described options ranging from low risk upgrades to the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) to higher risk game changing designs with efficiency above 10% and power density above 5 W/kg. While the latter are very compelling to the mission planners, the reality is that only the former is within reach of the current NASA budget and near term missions. System design and mission studies have determined that even the former approach will provide significant power system improvements for future missions. A program is therefore in progress to evaluate evolutionary MMRTG upgrades using new skutterudite (SKD) thermoelectric materials. Modest temperature increases to produce higher beginning of life (BOL) power from the SKD materials are expected to be within the capability of the MMRTG system design. The SKD materials are also expected to provide a substantial end of life (EOL) improvement relative to MMRTG materials. This paper examines the evolutionary system design changes for this enhanced (e)MMRTG, provides a risk assessment of each and summarizes the expected performance.